<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Align HTML Elements w/hiding</title>
    <style>
    html, body {
        margin: 0;
        height: 100%;
    }
    #c {
        width: 100%;  /* let our container decide our size */
        height: 100%;
        display: block;
    }
    #container {
      position: relative;  /* makes this the origin of its children */
      width: 100%;
      height: 100%;
      overflow: hidden;
    }
    #labels {
      position: absolute;  /* let us position ourself inside the container */
      left: 0;             /* make our position the top left of the container */
      top: 0;
      color: white;
    }
    #labels>div {
      position: absolute;  /* let us position them inside the container */
      left: 0;             /* make their default position the top left of the container */
      top: 0;
      cursor: pointer;     /* change the cursor to a hand when over us */
      font-size: large;
      user-select: none;   /* don't let the text get selected */
      text-shadow:         /* create a black outline */
        -1px -1px 0 #000,
         0   -1px 0 #000,
         1px -1px 0 #000,
         1px  0   0 #000,
         1px  1px 0 #000,
         0    1px 0 #000,
        -1px  1px 0 #000,
        -1px  0   0 #000;
    }
    #labels>div:hover {
      color: red;
    }
    </style>
  </head>
  <body>
    <div id="container">
      <canvas id="c"></canvas>
      <div id="labels"></div>
    </div>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 1.1;
	const far = 20;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.z = 7;

	const controls = new OrbitControls( camera, canvas );
	controls.target.set( 0, 0, 0 );
	controls.update();

	const scene = new THREE.Scene();

	{

		const color = 0xFFFFFF;
		const intensity = 3;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( - 1, 2, 4 );
		scene.add( light );

	}

	const boxWidth = 1;
	const boxHeight = 1;
	const boxDepth = 1;
	const geometry = new THREE.BoxGeometry( boxWidth, boxHeight, boxDepth );

	const labelContainerElem = document.querySelector( '#labels' );

	function makeInstance( geometry, color, x, name ) {

		const material = new THREE.MeshPhongMaterial( { color } );

		const cube = new THREE.Mesh( geometry, material );
		scene.add( cube );

		cube.position.x = x;

		const elem = document.createElement( 'div' );
		elem.textContent = name;
		labelContainerElem.appendChild( elem );

		return { cube, elem };

	}

	const cubes = [
		makeInstance( geometry, 0x44aa88, 0, 'Aqua' ),
		makeInstance( geometry, 0x8844aa, - 2, 'Purple' ),
		makeInstance( geometry, 0xaa8844, 2, 'Gold' ),
	];

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	const tempV = new THREE.Vector3();
	const raycaster = new THREE.Raycaster();

	function render( time ) {

		time *= 0.001;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		cubes.forEach( ( cubeInfo, ndx ) => {

			const { cube, elem } = cubeInfo;
			const speed = 1 + ndx * .1;
			const rot = time * speed;
			cube.rotation.x = rot;
			cube.rotation.y = rot;

			// get the position of the center of the cube
			cube.updateWorldMatrix( true, false );
			cube.getWorldPosition( tempV );

			// get the normalized screen coordinate of that position
			// x and y will be in the -1 to +1 range with x = -1 being
			// on the left and y = -1 being on the bottom
			tempV.project( camera );

			// ask the raycaster for all the objects that intersect
			// from the eye toward this object's position
			raycaster.setFromCamera( tempV, camera );
			const intersectedObjects = raycaster.intersectObjects( scene.children );
			// We're visible if the first intersection is this object.
			const show = intersectedObjects.length && cube === intersectedObjects[ 0 ].object;

			if ( ! show || Math.abs( tempV.z ) > 1 ) {

				// hide the label
				elem.style.display = 'none';

			} else {

				// unhide the label
				elem.style.display = '';

				// convert the normalized position to CSS coordinates
				const x = ( tempV.x * .5 + .5 ) * canvas.clientWidth;
				const y = ( tempV.y * - .5 + .5 ) * canvas.clientHeight;

				// move the elem to that position
				elem.style.transform = `translate(-50%, -50%) translate(${x}px,${y}px)`;

			}

		} );

		renderer.render( scene, camera );

		requestAnimationFrame( render );

	}

	requestAnimationFrame( render );

}

main();
</script>
</html>
